1. Field of the Invention
This invention relates to a method and apparatus for applying a layer of unvulcanised rubber, thermoplastic or similar material to a cylindrical workpiece, e.g. a steel roller.
Throughout this specification the term `rubber` will be used to mean unvulcanised rubber, thermoplastic or similar material and the term workpiece will be used to mean any cylindrical body which requires to be covered with an even layer of rubber material.
2. Description of the Prior Art
Known methods of roller covering are either labour intensive (e.g. building pre-extruded or pre-callendered sheet onto the workpiece by hand, either as one piece or in strips or layers) or may require expensive and complex capital equipment (e.g. special extruders designed to extrude rubber directly onto the workpiece). These known methods also suffer from particular deficiencies in that it is often difficult to avoid the inclusion of air blisters as the rubber is applied and it is only possible to achieve a rough surface finish. Both of these classes of deficiency can create a high production reject rate and call for a high volume of secondary finishing work (e.g. surface grinding) in order to produce satisfactory finished goods.